A Student Management System

1. Overview

The kernel of RaspberryPi runs the Linux operating system, which is the largest open source operating system and can fully support the operation of servers and programming scripts. In this project, we choose python and the corresponding Django framework because it is open source and stable [5]. In terms of databases, SQLite3 and SQLite3 are embedded databases in Django. When receiving a request from the client, Django will extract the corresponding data from the database or store the submitted data, and feed the corresponding information back to the front end or client of the student management system.

2. Django Installing

Pyhton is installed in RPi in advanced, so we just need to install Django. Before installing it. We can set up virtualenv at first, virtualenv creates a virtual environment separated from the system environment so that any operation here will not affect the RPi.
To install Django systemwide, use this command:
pip3 install Django
This command will start a new project:
django-admin startproject Management_system
When we run here for the first time, the system prompts "command not found: django-admin". The reason for the error is that django-admin did not join the system path. This can be done by symbolically linking the django-admin in the python.path/site-packages/django/bin/ folder to the /usr/local/bin file [6]. Or use the absolute path to run the command to create the project.
After completing the above operations, we have created a Django project. A folder with the same name will appear under this directory, which contains the server configuration file settng.py, and the routing configuration file urls.py. Then, we can create an application that actually runs the server:
python3 manage.py startapp mysystem
This will create another folder dedicated to storing project-related configuration files. For example, models.py defines the structure of the database [7]. Here, you can customize the tables and their attributes that you need to use. In this project, we created a total of six tables to store the corresponding data. Whenever a new table is created or form properties are updated, we need to connect the database to the backend. After connection, the changed content will be combined in the back-end processing model. The connection code is as follows:
python3 manage.py makemigrations
python3 manage.py migrate

3. Handle Requests

In the Django framework, different functions defined in the View.py script will process all requests according to different request destination addresses. When the web front end or RPi client sends a request, the requested data is packaged into a json file, encoded in utf-8. This file will send data to the corresponding url through the POST method, and call the corresponding function in view.py. We encountered two problems when processing POST requests. The first one is that Django always displays the error: Forbidden (403) at the beginning. The cause of the problem is the lack of CSRF token. But this application does not actually need a token, so this error can be avoided by simply placing a @csrf_exempt before the function that processes the request. The second problem is that sending json data must be passed in the form of a dictionary, otherwise an error will be reported

4. Networking

The server can be launched using this command:
python3 manage.py runserver &
This will allow the server to run in the background so that it can make room for the teacher user interface in the foreground.
We choose TCP for the communication between the two processes to achieve real-time updates of the database and avoid process conflicts.
Then we use:
python3 manage.py runserver 0.0.0.0:8000
This command will become the accessible address of the server on port 8000 of each ip address of the host, so that the server can be accessed by the external network. At the same time, we modify the corresponding settings in setting.py.